Polymers with a saturated hydrocarbon backbone are well known to possess good environmental and aging resistance which makes them highly desirable in a variety of applications. Furthermore, rubbery copolymers containing major amounts of polyisobutylene are well known to possess low permeability, unique damping properties, and low surface energy, which makes them particularly highly desired in many applications. However, the “inertness” of these saturated hydrocarbon polymers, their low reactivity and incompatibility with most other materials, and the difficulties in adhering them to, or using them in conjunction with most other materials has restricted their use in many areas.
Polymer compositions having low gas permeability, unique damping properties, and low surface energy are useful in applications such as tire innerliners. U.S. Pat. No. 5,162,445 discloses a method to improve polymer blend compatibility or blend co-curability by copolymerizing an unsaturated comonomer and/or a comonomer having reactive functionality with isobutylene. One example of such a polymer is a partially brominated copolymer of isobutylene and p-methylstyrene (BIMS). U.S. Pat. No. 5,548,029 discloses graft copolymers of isobutylene-p-methylstyrene copolymers to compatibilize blends of saturated and unsaturated elastomers.
The isobutylene-p-methylstyrene copolymers, a variety of functionalized derivatives thereof, and BIMS in particular, are useful in clay nanocomposites. See, for example, commonly assigned U.S. application Ser. No. 11/183,361, Split-Stream Process for Making Nanocomposites, by W. Weng et al., filed Jul. 18, 2005; and commonly assigned U.S. application Ser. No. 11/184,000, Functionalized Isobutylene Polymer-Inorganic Clay Nanocomposites and Organic-Aqueous Emulsion Process, by W. Weng et al., filed Jul. 18, 2005, the entirety of which are incorporated by reference.
The isobutylene-p-methylstyrene copolymers disclosed in the above listed patents typically have narrow molecular weight distributions (Mw/Mn<2.5), limiting green strength, and slow relaxation times that are not conducive to processability of the uncured formulations.
On the other hand, unsaturated isobutylene rubbers such as isobutylene—isoprene copolymers are known for generally difficult filler dispersion, e.g. they form poor nanocomposites with clay relative to PIBS. Isobutylene—isoprene copolymers typically have much broader molecular weight distributions than do the isobutylene para-methylstyrene copolymers. U.S. Pat. No. 6,841,642 to Kaszas (WO02/16452) discloses a polymer formed by reaction of a mixture of isobutylene, isoprene, divinylbenzene and a chain transfer agent, the entirety of which is incorporated by reference. Incorporation of DVB to the isobutylene—isoprene copolymer with the chain transfer agent is said to increase the viscosity and elasticity of the polymer at very low shear rates and to reduce the viscosity and elasticity at high shear rates, providing a butyl polymer having an improved balance of (more resistance to) cold flow, (higher degree of) filler dispersion, (higher) extrusion rate and (reduced) die swell.
A process for preparing rubbery polymers and copolymers in fluorinated hydrocarbon solvents is disclosed in WO 2004/058828, published Jul. 15, 2004, the entirety of which is incorporated by reference. Compared to chlorinated hydrocarbon solvents used in the polymerization of isobutylene-isoprene copolymers, the fluorinated hydrocarbon solvents generally produce butyl polymers with a narrower molecular weight distribution or polydispersity (Mw/Mn).
There exists a need to improve the ability to process the saturated isobutylene based polymers and polymer blends, including improvements in green strength, polymer compatibility, co-curability, and relaxation balance/times, while maintaining aging resistance, filler dispersibility, air barrier, and other desirable characteristics.